1. Field of the Invention
The present invention relates generally to an antenna, and more particularly to a multi-band antenna used for electronic devices, such as notebook.
2. Description of Prior Art
With the high-speed development of the mobile communication, people more and more expect to use a computer or other portable terminals to optionally connect to Internet. GPRS (General Packer Radio Service) and WLAN (Wireless Local Area Network) allow users to access data wirelessly over both cellular networks and 802.11b WLAN system. When operating in GPRS, the data transmitting speed is up to 30 Kbps˜50 Kbps, while when connected to a WLAN access point, the data transmitting speed is up to 11 Mbps. People can select different PC cards and cooperate with the portable terminals such as the notebook computer or the like. to optionally connect to Internet. Since WLAN has a higher transmitting speed, WLAN is usually used to provide public WLAN high-speed data services in some hot areas (for example, hotel, airport, coffee bar, commerce heartland, conference heartland and etc.). When leaving from these hot areas, network connection is automatically switched to GPRS.
As it is known to all, an antenna plays an important role in wireless communication. As a result, the PC card may choose individual antennas to respectively operate at WWAN (Wireless Wide Area Network), namely GPRS, and WLAN. It arises a hot problem to integrate two individual antennas in a limited space to go along with the miniaturization of portal devices. Please refer to FIG. 1, a multi-band antenna 10′ comprises a first type of antenna which is used in WWAN and has first and second antennas 1′, 2′ and a second type of antenna which is used in WLAN and has third and fourth antennas 3′, 4′. The multi-band antenna 10′ is integrally made from a metal sheet and integrates the first type of antenna for WWAN and the second type antenna for WLAN together. However, with the two types of antennas integration, the interference therebetween will become greater, and owing to this structure, the antenna 1′ can not achieve enough bandwidth. Hence, it is necessary to be concerned by researchers skilled in the art how to incorporate two antennas respectively operating at WWAN and WLAN into a single antenna while keeping enough bandwidth and low interference.